1. Field of the Invention
The present invention relates to magnetic detecting elements that utilize a tunneling effect and are mounted on hard disk apparatuses and other magnetic detecting apparatuses. In particular, it relates to a tunneling magnetic detecting element in which the rate of change in resistance (ΔR/R) is improved, and a method for making such a tunneling magnetic detecting element.
2. Description of the Related Art
A tunneling magnetoresistive element uses a tunneling effect to generate changes in resistance. The resistance peaks when the magnetization direction of the pinned magnetic layer and the magnetization direction of the free magnetic layer are antiparallel to each other. This is because the tunneling current does not smoothly flow due to an insulating barrier layer (tunneling barrier layer) formed between the pinned magnetic layer and the free magnetic layer. In contrast, the resistance is minimum when the magnetization direction of the pinned magnetic layer and the magnetization direction of the free magnetic layer are parallel to each other since the tunneling current smoothly flows under such a condition.
Under this principle, changes in electrical resistance caused by changes in magnetization direction of the free magnetic layer under application of external magnetic fields can be detected as changed in voltage, and this principle is now used to detect leakage magnetic fields from recording media.
In order to improve the rate of change in resistance (ΔR/R) of a tunneling magnetic detecting element, for example, the material of the free magnetic layer in contact with the insulating barrier layer is changed from a material that has been used in the related art. For example, a free magnetic layer is formed to include a soft magnetic sublayer composed of Ni—Fe and an enhancing sublayer composed of Co—Fe and in contact with the insulating barrier layer while being disposed between the soft magnetic layer and the insulating barrier layer. The rate of change in resistance (ΔR/R) can be increased by increasing the Fe concentration in Co—Fe constituting the enhancing layer.
However, increasing the Fe concentration in the enhancing layer increases the magnetostriction of the free magnetic layer and degrades operation stability, which has been a problem.
Thus, it is now desired to increase the rate of change in resistance (ΔR/R) without changing the configuration of the free magnetic layer or the pinned magnetic layer. PCT Japanese Translation Patent Publication No. 2000-508834 and Japanese Unexamined Patent Application Publication Nos. 2006-520105 and 2003-204045 each disclose a tunneling magnetic detecting element and the material of the insulating barrier layer.
However, none of the patent documents described above discloses a structure that achieves an increased rate of change in resistance (ΔR/R) without changing the configuration of the free magnetic layer or the pinned magnetic layer.